Many sorts of things. Products ("to produce everything from mattresses, spectacles,road signs and body armour"), agriculture and firefighting through "convict leasing" programs ("Convict leasing was largely banned in the 20th century, but has once more grown in popularity as immigrant labor has become harder to find. Multiple states have now passed legislation allowing agricultural businesses to use prison labor when they cannot find enough workers to hire, and most prison workers are paid significantly less than non-prison labor.").

It's rather widespread.

> In addition to the South Carolina inmates who were hired by a subcontractor in the 1990s to stitch Victoria's Secret lingerie, prisoners in the past two decades have packaged or assembled everything from Starbucks coffee beans to Shelby Cobra sports cars, Nintendo Game Boys, Microsoft mouses and Eddie Bauer clothing. Inmates manning phone banks have taken airline reservations and even made calls on behalf of political candidates.

Earlier this month, we doubled the number of states to have banned involuntary labor in prison … bringing it up to a heady eight, if challenges don't roll any back. We need more states to do so, and the Federal system as well.